EvidenceDPreliminaryVery uncertain: animal or cell studies, or studies in people with several serious weaknesses.
We don't know yet whether methylene blue improves everyday memory. Small, short trials hint at memory gains after a single low dose, and one found it could backfire.
Who it's for
No group has a clear benefit; not shown to help healthy adults' memory.
What to expect
Small, short-lived changes in lab memory tests; no proven everyday gain.
Watch out for
Dangerous interactions with antidepressants and some other drugs, plus a blood-cell risk.
What the studies show
A trial of 42 adults with claustrophobia gave 260 mg of methylene blue or a dummy pill (placebo A dummy treatment that looks like the real one, so people can't tell which they got.) after fear-exposure training. Methylene blue improved memory for the setting of the training, whatever the person's fear level1Randomized trial · 2014 · 23 peopleEffects of post-session administration of methylene blue on fear extinction and contextual memory in adults with claustrophobia.Methylene blue enhances memory and the retention of fear extinction when administered after a successful exposure session but may have a deleterious effect on extinction when administered after an unsuccessful exposure session.Am J Psychiatry. Fear results were mixed: people with low fear after training did better a month later, while those with moderate to high fear tended to do worse1Randomized trial · 2014 · 23 peopleEffects of post-session administration of methylene blue on fear extinction and contextual memory in adults with claustrophobia.Methylene blue enhances memory and the retention of fear extinction when administered after a successful exposure session but may have a deleterious effect on extinction when administered after an unsuccessful exposure session.Am J Psychiatry.
A second scan trial in healthy adults found one low dose changed blood flow and strengthened connections between brain regions tied to perception and memory3Randomized trial · 2017Methylene blue modulates functional connectivity in the human brain.These findings demonstrate for the first time that low-dose MB can modulate task-related and resting-state neural networks in the human brain. These neuroimaging findings support further investigations in healthy and disease populations.Brain Imaging Behav. It did not test memory in daily life.
A trial of 42 people with long-standing PTSD paired exposure therapy with 260 mg of methylene blue or a placebo. Methylene blue improved treatment response modestly, and about 7 or 8 people needed treatment for one extra person to respond4Randomized trial · 2017 · 42 peopleEnhancing Extinction Learning in Posttraumatic Stress Disorder With Brief Daily Imaginal Exposure and Methylene Blue: A Randomized Controlled Trial.The findings provide preliminary efficacy for a brief IE treatment for PTSD and point to the potential utility of MB for enhancing outcome. Brief interventions and better tailoring of MB augmentation strategies, adjusting for observed patterns, may have the potential to reduce dropout, accelerate change, and improve…J Clin Psychiatry. This tested PTSD recovery, not memory in healthy people.
Reviews describe memory benefits mainly from animal and mechanism work5Review · 2012Neurometabolic mechanisms for memory enhancement and neuroprotection of methylene blue.The unique auto-oxidizing property of methylene blue and its pleiotropic effects on a number of tissue oxidases explain its potent neuroprotective effects at low doses. The evidence reviewed supports a mechanistic role of low-dose methylene blue as a promising and safe intervention for improving memory and for the…Prog Neurobiol,6Review · 2021The Potentials of Methylene Blue as an Anti-Aging Drug.MB can bypass Complex I/III activity in mitochondria and diminish oxidative stress to some degree. This review summarizes the recent studies on the applications of MB in treating age-related conditions, including neurodegeneration, memory loss, skin aging, and a premature aging disease, progeria.Cells. A review of Alzheimer's studies reports cognitive gains, but the strongest support there is from animals8Review · 2023Exploring Methylene Blue and Its Derivatives in Alzheimer's Treatment: A Comprehensive Review of Randomized Control Trials.The findings of the studies indicate that the administration of MB has demonstrated enhancements in cognitive function, reductions in the accumulation of plaques containing beta-amyloid, improvements in memory and cognitive function in animal subjects, and possesses antioxidant properties that can mitigate oxidative…Cureus. A mouse study found a related compound reversed drug-induced memory problems9Animal study · 2026Effects of hydromethylthionine mesylate and rivastigmine in a pharmacological mouse model of Alzheimer's disease.Furthermore, coadministration of rivastigmine with HMTM ameliorated the impairments induced by scopolamine. These findings extend our previous observations with MTC and confirm that HMTM also has a dual mode of action, disease modification through tau aggregation inhibition, but also having symptomatic effects through…Behav Pharmacol.
Key studies
Study
Who
What it found
Trial, 20141Randomized trial · 2014 · 23 peopleEffects of post-session administration of methylene blue on fear extinction and contextual memory in adults with claustrophobia.Methylene blue enhances memory and the retention of fear extinction when administered after a successful exposure session but may have a deleterious effect on extinction when administered after an unsuccessful exposure session.Am J Psychiatry
42 adults with claustrophobia
Better contextual memory; fear results varied by fear level
More brain activity; 7% more correct memory answers
Trial, 20173Randomized trial · 2017Methylene blue modulates functional connectivity in the human brain.These findings demonstrate for the first time that low-dose MB can modulate task-related and resting-state neural networks in the human brain. These neuroimaging findings support further investigations in healthy and disease populations.Brain Imaging Behav
Healthy adults
Changed brain connectivity one hour after one dose
Trial, 20174Randomized trial · 2017 · 42 peopleEnhancing Extinction Learning in Posttraumatic Stress Disorder With Brief Daily Imaginal Exposure and Methylene Blue: A Randomized Controlled Trial.The findings provide preliminary efficacy for a brief IE treatment for PTSD and point to the potential utility of MB for enhancing outcome. Brief interventions and better tailoring of MB augmentation strategies, adjusting for observed patterns, may have the potential to reduce dropout, accelerate change, and improve…J Clin Psychiatry
42 adults with PTSD
Modestly better therapy response with methylene blue
Safety
The injectable drug carries a boxed warning for serotonin syndrome, which can be serious or fatal, when combined with SSRIs, SNRIs, MAOIs and opioids10Guideline · 2025Methylene Blue: FDA drug label (prescribing information)Contraindications: Methylene blue injection is contraindicated in the following conditions: Severe hypersensitivity reactions to methylene blue or any other thiazine dye . Patients with glucose-6-phosphate dehydrogenase deficiency (G6PD) due to the risk of hemolytic anemia . Methylene blue injection is contraindicat…US Food and Drug Administration. It is contraindicated in people with G6PD deficiency because of the risk of destroyed red blood cells (hemolytic anemia), and in people with severe allergy to it10Guideline · 2025Methylene Blue: FDA drug label (prescribing information)Contraindications: Methylene blue injection is contraindicated in the following conditions: Severe hypersensitivity reactions to methylene blue or any other thiazine dye . Patients with glucose-6-phosphate dehydrogenase deficiency (G6PD) due to the risk of hemolytic anemia . Methylene blue injection is contraindicat…US Food and Drug Administration. A review notes it blocks monoamine oxidase A, so caution is needed7Review · 2019Methylene Blue in the Treatment of Neuropsychiatric Disorders.Long-term use of methylene blue in bipolar disorder led to a better stabilization and a reduction in residual symptoms of the illness. It is usually well tolerated, but caution is needed in the light of its inhibitory effect on monoamine oxidase A.CNS Drugs. Methylene blue is an approved drug for blood disorders and poisonings, not for memory.
What we don't know
Whether any memory benefit lasts, or shows up in daily life, since trials were small and brief.
Which dose is safe and useful for memory. A review describes opposite effects at low and high doses5Review · 2012Neurometabolic mechanisms for memory enhancement and neuroprotection of methylene blue.The unique auto-oxidizing property of methylene blue and its pleiotropic effects on a number of tissue oxidases explain its potent neuroprotective effects at low doses. The evidence reviewed supports a mechanistic role of low-dose methylene blue as a promising and safe intervention for improving memory and for the…Prog Neurobiol. A 117-person trial in healthy aging, mild cognitive impairment and Alzheimer's has been completed11Registered trial · 2015Effects of Methylene Blue in Healthy Aging, Mild Cognitive Impairment and Alzheimer's DiseaseClinicalTrials.gov.
Written by AI from the studies listed, without review by a clinician, and graded with the GRADE method. It can be wrong, so check the studies it cites. Education, not medical advice.